The present invention relates to a semiconductor module including therein a semiconductor element, for example, a semiconductor transistor, thyristor and/or diode, and an inverter device including the semiconductor module.
JP-A-8-111503 discloses a semiconductor module including an electric insulating plate between an emitter terminal and a collector terminal.
An object of the present invention is to provide a semiconductor module and an inverter device, by which an electrical insulation relative to an electrically grounded surface is reinforced, and an inductance between input and output terminals thereof is decreased.
A semiconductor module according to the invention, comprises, a semiconductor element, an electrically insulating base having an outer surface to be connected to an electrically grounded surface, and an inner surface on which the semiconductor element is arranged, an electrically insulating cover covering the semiconductor element on the inner surface, and first and second electrically conductive members each of which is connected to the semiconductor element and extends to the exterior of the semiconductor module through the electrically insulating cover, wherein a part of each of the first and second electrically conductive members on the exterior of the semiconductor module is arranged away from the outer surface to electrically isolate the part of the each of the first and second electrically conductive members from the electrically grounded surface. Therefore, an electrical insulation of the first and second electrically conductive members relative to the electrically grounded surface is securely kept.
When an electric current is supplied to the semiconductor element through the first electrically conductive member, and at least a part of the electric current is output from the semiconductor module through the second electrically conductive member, and the first and second electrically conductive members are arranged close to each other to form a mutual inductance therebetween, an inductance of the semiconductor module between the parts of the first and second electrically conductive members is decreased by the mutual inductance.
When a third electrically conductive member is connected to the semiconductor element and extends to the exterior of the semiconductor module through the electrically insulating cover, a value of electric current flowing through the third electrically conductive member is significantly smaller than a value of electric current flowing through the each of the first and second electrically conductive members, a part of the third electrically conductive member on the exterior of the semiconductor module is arranged away from the outer surface to electrically isolate the part of the third electrically conductive member from the electrically grounded surface, and a distance between the outer surface and the part of the third electrically conductive member is not less than 80% of a distance between the outer surface and the part of the each of the first and second electrically conductive members in a direction perpendicular to the outer surface, all of the parts of the first, second and third electrically conductive members are securely isolated electrically from the electrically grounded surface.
If a first electrically insulating spacer is inserted in jelly-state into a space between the semiconductor element and the electrically insulating cover and cured between the semiconductor element and the electrically insulating cover, and a second electrically insulating spacer is inserted in solid-state between areas of the first and second electrically conductive members facing close to each other to form a mutual inductance therebetween, the space complex in shape between the semiconductor element and the electrically insulating cover is securely filled by the first electrically insulating spacer in jelly-state cured after filling the space, and the areas of the first and second electrically conductive members facing close to each other to form the mutual inductance therebetween are securely isolated electrically from each other by the second electrically insulating spacer inserted in solid-state therebetween without voids of the first electrically insulating spacer in jelly-state. Between the second electrically insulating spacer and each or one of the areas of the first and second electrically conductive members, the first electrically insulating spacer in jelly-state may be inserted.
When at least one of the first and second electrically conductive members includes a first bent portion, a second bent portion and a third bent portion arranged in series while the second bent portion is arranged between the first and third bent portions in a current flow direction in which an electric current flows, the first, second and third bent portions are bent around respective axes parallel to each other and perpendicular to a thickness direction of the at least one of the first and second electrically conductive members at the first, second and third bent portions, and a portion of the at least one of the first and second electrically conductive members between the first and third bent portion is prevented from contacting with an electrically insulating member such as the electrically insulating cover, the cured first electrically insulating spacer and/or the electrically insulating base, the at least one of the first and second electrically conductive members is restrained effectively from generating a large stress caused by an undesirable deformation of the semiconductor module.
If the first and second electrically conductive members have respective relatively-wide portions facing close to each other, and a directional component of electric current in one of the relatively-wide portions is opposite to another directional component of electric current in another one of the relatively-wide portions, the mutual inductance is effectively increased. If the first and second electrically conductive members have respective relatively-narrow portions adjacent to the relatively-wide portions, and a cross-sectional area of each of the relatively-wide portions is larger than that of each of the relatively-narrow portions as seen in a current flow direction in which an electric current flows to concentrate the electric current to areas of the relatively-wide portions adjacent to the relatively-narrow portions, the mutual inductance is more effectively increased. If at least one of the first and second electrically conductive members is bent at the relatively-narrow portion around an axis perpendicular to a thickness direction of the at least one of the first and second electrically conductive members at the relatively-narrow portion, the mutual inductance is more effectively increased. The at least one of the first and second electrically conductive members may have at least two connecting feet each of which projects divergently from the relatively-narrow portion and is connected to the semiconductor element so that the mutual inductance is formed between the relatively-wide portion and the connecting foot both adjacent to the relatively-narrow portion. If the at least two connecting feet adjacent to the relatively-narrow portions extend substantially parallel to the part of each of the first and second electrically conductive members on the exterior of the semiconductor module, the mutual inductance is further increased. If a flowing direction of electric current is bent by the relatively-narrow portion of at least one of the first and second electrically conductive members to increase a length of electric current path between the part of the at least one of the first and second electrically conductive members and the semiconductor element and to make the flowing direction of electric current from the relatively-narrow portion and the flowing direction of electric current to the relatively-narrow portion opposite to each other, the mutual inductance is further increased. If one of the relatively-wide portions is bent to partially surround partially another one of the relatively-wide portions so that the one of the relatively-wide portions extends over or faces to both side surfaces of the another one of the relatively-wide portions, the mutual inductance is effectively increased.
As seen in a direction perpendicular to the outer surface, the relatively-wide portions may face to each other in a direction substantially perpendicular to an imaginary line extending between the parts of the first and second electrically conductive members on the exterior of the semiconductor module. A distance between the part of the third electrically conductive member and the part of the each of the first and second electrically conductive members in the direction parallel to the outer surface may be not less than 5 mm.
If both of the first and second electrically conductive members extend from the exterior of the semiconductor module toward the relatively-wide portions to flow respective electric currents obliquely to a direction perpendicular to the outer surface between the exterior of the semiconductor module and the relatively-wide portions, the electric currents crossing each other as seen in the thickness direction of the first and second electrically conductive members forms the mutual inductance therebetween.
A distance between the outer surface and the part of each of the first and third electrically conductive members may be less than a distance between the outer surface and the part the second electrically conductive members in a direction perpendicular to the outer surface.
According to the invention, an inverter device or semiconductor module assembly comprises a pair of first and second semiconductor modules each comprising, semiconductor elements, an electrically insulating base having an outer surface to be connected to an electrically grounded surface, and an inner surface on which the semiconductor element is arranged, an electrically insulating cover covering the semiconductor elements on the inner surface, and first and second terminal surfaces adapted to be contacted with a bus bar to form an electric communication between the semiconductor elements and the bus bar, wherein an electric current flows into the first and second terminal surfaces of the first semiconductor module from one of the bus bars, at least a part of the electric current flows out of the first and second terminal surfaces of the second semiconductor module into another one of the bus bars, the first and second terminal surfaces of the first semiconductor module and the first and second terminal surfaces of the second semiconductor module are arranged along a substantially straight imaginary line as seen in a direction perpendicular to the outer surfaces, and a height between the outer surface and an imaginary plane on which the first and second terminal surfaces of the first semiconductor module extend is different from a height between the outer surface and another imaginary plane on which the first and second terminal surfaces of the second semiconductor module extend as seen in a direction parallel to the outer surfaces, so that the bus bars can extend parallel to each other and face to each other to decrease an inductance of the bus bars by forming form a mutual inductance between the bus bars.